The invention relates to a rotary piston engine according to the class of the main claim. In the case of one rotary piston machine, which is known from prior art and is of the kind which is class-specific to the patent publication WO2005/024237 A1 of the World Intellectual Property Organization, the applicant particularly emphasizes the advantageous fact that a relevant housing unit for the electric motor and the pump can be of small design. This is due to the electric motor directly engaging the power component of the rotors on the blocking component side without any additional costly bearing support. The housings can be embodied extremely simply and connected to one another. This is especially important for applications in fuel delivery systems of internal combustion engines, for example as a prefeed pump, wherein a very important quiet running of the engine is achieved with the rotary piston engine according to the invention. Said quiet running of the engine is particularly important for motor vehicle applications. In each case, the mounting and disposal of the power component with respect to the axis of rotation of the electric motor is extremely important and also that which relates to the relative axial displaceability of said power component. Such a housing unit can also be easily adapted to the requirements with regard to the gearing and the output thereby achieved.